Which three statements about OSPF areas are true?（）

• A、Areas introduce a boundary on the link - state updates.
• B、Areas are  logical definitions specific to any given router.
• C、All routers within an area have the exact link - state database.
• D、The calculation of the Dijkstra algorithm on a router is limited to changes within an area.
• E、The area designated router will always  have a priority of 0.